Gas-Phase Alloying and Sintering Kinetics of 3D Printed Ni Scaffolds

具有越来越复杂的几何形状的金属部件的制造是几个行业感兴趣的。特别是，金属支架由于其低密度和高表面积，是从电池到生物医学植入物的各种应用的良好候选者。然而，许多技术上重要的合金很难使用传统制造方法在支架几何形状中制造，甚至较新的方法，如增材制造（通常称为3D打印），也面临着重大挑战。一种新的工艺已经被理论化，通过两步方法制造这些金属支架，这将使各种不同的材料能够从相同的前体印刷金属部件中生产出来。该奖项支持研究，以了解控制这一新过程的动力学和热力学的基本机制。由于金属支架结构的广泛工程应用，这项研究的结果将促进包括能源，汽车和生物医学行业在内的许多制造业领域的技术创新。通过招聘和推广活动，传统上代表性不足的STEM群体将参与这项研究工作，这将吸引学生在早期参与，并有助于使工程职业管道多样化。虽然创造具有高度几何复杂性的近净形金属零件的能力使粉末床增材制造技术具有吸引力，许多工程相关合金由于烧结不良、内部孔隙和开裂而难以高质量地制造。一种替代方法是通过使用基于颗粒的油墨印刷来分离印刷和合金化，以从已知成功印刷的纯金属或简单合金产生期望的几何形状，然后在单独的步骤中使用沉积工艺和均质化来进一步合金化部件以达到目标成分。这种方法是理想的创造金属支架，利用开放的孔隙率和小的扩散距离。该项目的总体目标是研究基本的烧结和合金化动力学的这种支架使用传统的金相和原位X射线断层扫描显微镜相结合。将系统地研究相和孔的演变作为几何形状、成分、粉末和支柱尺寸以及退火时间和温度的函数，并且将通过计算预测和实验确定机械行为。

The fabrication of metal parts with increasingly complex geometries is of interest to several industries. In particular, metal scaffolds are good candidates for a variety of applications from batteries to biomedical implants, due to their low density and high surface area. However, many technologically important alloys are difficult to fabricate in scaffold geometries using traditional manufacturing, and even newer approaches such as additive manufacturing (often known as 3D printing), have significant challenges. A new process has been theorized for making these metal scaffolds through a two-step approach, which will enable an assortment of different materials to be produced from the same precursor printed metal part. This award supports research to understand the fundamental mechanisms of kinetics and thermodynamics that control this new process. Because of the wide range of engineering applications for metal scaffold structures, results from this research will promote technological innovations in a number of manufacturing sectors including energy, automotive and biomedical industries. Through recruiting and outreach activities, traditionally underrepresented groups in STEM will be involved in this research effort, which will engage students at an early age and help diversify the engineering career pipeline.While the ability to create near-net-shape metallic parts with high geometric complexity has made powder-bed additive manufacturing techniques attractive, many engineering relevant alloys are difficult to fabricate with high quality due to poor sintering, internal porosity, and cracking. One alternative approach is to decouple the printing and alloying by using particle-based ink printing to create the desired geometry from a pure metal or simple alloy that is known to print successfully, and then further alloy the part in a separate step using a deposition process and homogenization to reach the target composition. This approach is ideal for creating metallic scaffolds, taking advantage of the open porosity and small diffusion distances. The overall aim of this project is to study the fundamental sintering and alloying kinetics of such scaffolds using a combination of conventional metallography and in situ X-ray tomographic microscopy. The phase and pore evolution will be systematically studied as a function of geometry, composition, powder and strut size, and anneal time and temperature and the mechanical behavior will be computationally predicted and experimentally determined.